Process and apparatus for sealingoff vessels containing gas



Dec. 9, 1941. M. DE NEUMANN PROCESS AND APPARATUS FOR SEALING-OFF VESSELS CONTAINING GAS Filed June 19, 1937 Sheets-Sheet 1 De. 9, 1941. 35 NEUMANN 2,265,359

PROCESS AND APPARATUS FOR SEALING-OFF VESSELS CONTAINING GAS Fil ed June 19, 1957 2 Sheets-Sheet 2 Fig 1a.

lnvervtor ihalg deNeumann, b5 W His Attorneg.

Patented Dec.

UNITED STAT E PAT ENT OFFICE v NW ms a i .iipufstwn'iaine 11.9. innunxm'lunezo, 1936 acuims." (01.4942) This invention relates to a process and apparatus for sealing ofi .(that is tosay. eflf,ecting the air-tight closure of) vessels which are illled with gas and more particularly to the sealing off of gas-filledv electric incandescent lamps,- or dis: charge tubes, provided with anexhausting'and filling tube made of vitreous material, such as glass, by the sealing oil of which the closure of the bulb of the lamp, or tube is accomplished.

Numerous processes are known for achieving the above results and these include some which are suitablefor sealing ofl vesselsin whichthe filling gas pressure is higher than atmospheric pressure at the time of sealing off, some of these processes being described in myprevious Patents Nos. 1,977,671 and 2,014,471.

Those, of .the known processes in which. the exhausting tube, while in a heated condition, is pinched together by means of a tool, require a high degree of uniformity in thequality of the exhausting tubesand heating must be eifected by means of a precisely regulated flame fed with gas which is, carefully kept at constant pressure and uniform as to composition; furthermore, production has to be carried out under a very steady filling-gas pressure and on automatic machines running at carefully regulated speed. In producing lamps all of the same type, the fulfilment of these requirements involves no specialdifliculties, but if the type of lampbe changed it is necessary to carry out tedious tests. In one prior process in which the exhausting tube is pinched together with a sheath drawn over it, the dimculties referred to are certainly not present in such a marked degree, but the use of the sheath renders both the process and its product more expensive.

The process according'to the present invention is an improvement of those claimed in my previous patents mentioned above (and therefore also relates to the sealing-0d of vessels, which contain gas under pressure, greater than that of the atmosphere), and eliminates all the difficulties mentioned above by using, for the sealing ofi of the exhausting tube, a highly heated tool (1. e. heated at least to a bright red heat), which tool transmits to the said tube, mainly by direct transference, the main part'or all the heat requisite for softening the said tube and this bi-partite or multi-partite tool is allowed to cool down while in its contracted condition, that is to say, while it still remains in contact with the exhausting tube which it has already closed, cooling being continued until the tube is sufllciently hard not "preferably made resilient and/or is pressed to blow when the tool is opened. The tool is against the exhausting tube elastically, for exampleby means of springs, by compressed air orby other equivalent means. Preferably (although it is not absolutely necessary) the exhausting tube is pre heated before the tool is brought into con tact with it. This pre-heating avoids the risk of cracking when the glowingtool is pressed against the vitreous tube, but it can without danger be dispensed with if the heating of the tool is comparatively slow and is begun only after the tool has already been brought into contact with the tube. If this last-mentioned procedure be adopted,- the steady compressing, i. e. squeezing or pinching together of the exhausting tube will,

owing to the tool being elastically pressed against the tube, of necessity and automatically proceed in accordance with the rate of softening of the vitreous tube material, so that there will then be no risk of fracture or breakage, nor of blowing at the point where the tube is pinched. In view of the relatively low thermal conductivity of glass there is also but little risk of the tube softening to such an extent at any point lying outside the zone of action of the tool that a blow-out will occur at such point. This slight risk can, however, be eliminated entirely if the points in question are cooled in a suitable manner, as for instance, by a current of air. The tool itself may conveniently be heated either by passing an electric current through it or by means of heaters located on or in it or, either in place of or in addition to such methods of heating, it may be heated by means of a gas flame. The conjoint cooling of the tool and of the vitreous tube may, if necessary, be accelerated by means of a current of air or otherwise. I

The above described method of working is still attended by the difliculty that the highly heated tool (if it is not made of a suitable material and/or with a suitable external surface) has a tendency to stick to the glass and when an attempt is then made to detach it from the tube, after cooling down, the glass may crack or shatter, as a result. Experience has shown that tools made of a metal alloy containing chromium and iron and/or nickel are free from these disadvantages if their external surfaces are perfectly smooth and clean (e. g. bright or polished), but in certain cases good results can be obtained with tools of other suitable materials (e. g. graphite or carbon). In practice, however, the use of metal tools is more advantageous, notwithstanding the fact that the external surface of such a tool rapidly loses the properties above referred to as being to-satisfactory working. Even my invention, to obtain satisfactory results, if" that surface of the tool which comes into contact with the glass is coated, before eachpinching operatiomwith a layer of'a pulverulent, fireproof material, such as graphite, which may conveniently be applied in the form ofan aqueous suspension.

very suitable for thisv purpose.)

(The colloidal suspension marketed; under the registered trade-mark Aquadag'? is The risk of cracking or fracture, above referred to, canalso.

tools with rough and/or dirty (e. g. oxidized) surfaces'are employed, it is possible according to cal side view, the but generally usual, first stage of my process, the pre-heating of the glass tube to! thclamp bulb X provided with thestemYtowliichthetubelisfusedinthe usual way, being thereby connected with the bulb.

tube is connected by meansof the connecting-piece Z, made of rubber, to the-gas-supply-tube W,,this supply tube being connected to the gas-mains (not shown) supplying the gas, for example a mixture of argon and nitrogen, at

1 super-atmosphericpressure. The bulb Xbeing be avoided with perfect certaintyif, instead of or in addition to following the foregoing directions, tools are used which consist of amateriab Z the coefilcient of thermal'expanslon {of which. 1 corresponds, exactly or substantially, to, that of f the glass of the exhausting tube (the permissible 1 divergence being :15%, at most) and if the tool is removed from the surface of the pinched glass tube, when the same is already cooled down, such removal being preferably eflected either during a gradual change in the shape of the tool or after such a change of sham: has taken place. This can easily be arranged, for instance, when using tools of thin sheet material bent to shape. Both these and other tools may advantageously be so shapedfthat they actually ,part or sever the exhausting tubeafter they have pinched its walls together. Tools of a 'shape Q suitable for parting the tube are known from 1 I myprior patents already referred to.

The disadvantagethat the time required for 3 the cooling down of'the exhausting tube delays 1 the operation of the rotary automatic machines 3 used in practice for the production of incandescent lamps and discharge tubes can be overcome by my present invention by allowing the ala ready sealed-off vessel to be transferred to a separate and, auxiliary automatic machine by means of a sealing-off tool belonging to the said auxiliary machine and then parting thesealed 3 tube of the vessel on the auxiliary instead of on l the main automatic machine. In this way the j output at the parting-oi! position of rest of the automatic machine can be multiplied to the extent of the number of positions of rest available on the auxiliary automatic machine and production is accelerated instead of being delayed. The

process can be still further accelerated by using pinching tools of low thermal capacity, so that they heat up and cool down rapidly.

The process according to my invention and the apparatus for carrying it into efiect will now be more fully described, with reference to the accompanying drawings, in which:

Fig.1 shows the pre-heating of the tube oi an electric lamp,'and Fig. ia-is an elevation showing the pinching tools and actuating mechanism therefor. 1

Fig. 2 shows the beginning of the sealing-off process ,of the same tube.

Fig. 3 illustrates the manner of pinching and .of deforming the tool.

.Fig. 4 shows the sealed-off drawn tool.

Fig. 5 is a side view of a tool of modified shape.

tube, with the with- Fig. 6 is a plan view of another alternative T gtool arrangement. I Fig. 7.illustrates diagrammatically, in a plan 'view sketch, the process of producing, with the process according to my invention, gas-filled electric incandescent lamps on automatic machines.

Fig. 1 of the drawings shows, in a diagrammatitherefore filled with gas of superatmospheric pressure,- the gas flames of the gas burners m and 11 newly allowed to heat the tube I to a temperature below the softening point of the cleamess, the lamp bulb X with its stem Y, the

connecting-piece Z, the supply tube W and the means holding and rotating the whole assemblyin the automatic machineare not shown. The bipartite tool shown in this figure consists of two comparatively'thin U-shaped plates 2 and 3. of chromium nickel alloy whichhby means of jaws 2a, 2b and 3a, 3b, which embracetheir respective ends, can be pressed elastically to the tube. In that case springs, pneumatic cushions or the like (not shown) are connected between the jaws and the positively driven means which move the laws in the direction of the arrows 8 and 9 to compress the tube, and in the opposite directions to release the sealed tube. The two half tools are heated by means of electric, preferably alternating, current fed to them through the said jaws from a suitable source, such as a transformer I: (Fig. 1a), by means of leads ll connected to each of said jaws. The jaws are movable to and from each other, and are mounted on a pressure device containing the means mentioned above, and actuated by the automatic machine, this device of any suitable design not being shown in the drawings. The said pressure device may be pneumatic in itself or may comprise springs or the like arranged between its positively driven members and the jaws themselves, so that the tool elements are pressed resiliently against the tube I. The tube will be, in the next stage of the process, wherein the half-tools 2 and 3 are pressed-against the tube, wholly or partially heated to softening temperature by direct transmission of heat from the .tool elements which, during the pinching operation, are at a bright red heat and finally, when the glass becomes soft enough, the inner walls of the tube are simultaneously squeezed together until they weld up with each other.

It is preferable to cool the external parts of the tube lying near the zone of action of the tool by means of air blasts blowing from the nozzles 4, 5,411 and 5a in the direction of the arrows 4s, 5x, 41/ and 51 against the tube, 1. e. above and below the contacting points of the compressing tools, so that the tube cannot blow indicated by full lines'in Fig. 3 (Le. the position in which sealing off is completed, so that the bores la and lb of the tube no longer communicate with each other) the supply of heating current is cut oil and the tool, together with the tube, is allowed to cool down. The relative positions of the tool holding jaw 2a to the jaw 21) and that of the jaw 3a to the jaw 31) remain unchanged both during pinching and during cooling down.

When the cooling down process, slightly assisted in practice by the application of an air blast produced, for example, by altering at this stage of the process the positions of the air nozzles shown on Figure 2,'has proceeded far enough, so that there is no fear of a blow-out after the tool has been removed, the tool holding jaws are moved relatively to each other in such a way that the tool elements assume the form indicated by dotted lines 2:): and 3a: in Fig. 3, the radius of curvature of the tool ends thus being reduced. This materially facilitates the separation of the tool from the glass but, as has already been stated, separation can be still further assisted it, prior to the pinching operation, an aqueous suspension of graphite is applied to those surfaces of the tool which come into contact with the glass.

After or during their elastic deformation already described the tool elements are drawn apart as shown in Fig. 4, and thereafter, by suitably moving their jaws, are brought to their original shape and positions. The lower end of the tube, on the other hand, is usually broken off upon drawing the tools apart, or can be broken off later, the bore lb being in both cases preferably previously shut off from the source of filling gas.

If it is desired to use gas heating, in order to replace wholly or partially the expensive electric current, as the source of heat, each tool can be heated by means of gas flames emanating from the gas burners m and 11 shown in Fig. 1. In many cases, especially when gas heating is employed, it is preferable to use thin sheet metal tools of this kind which have suflicient inherent elasticity just to press the walls of the glass tube together after the tube has softened but not to break the tube. The breaking off of the lower end of the tube need not entail a separate operation if the toollll shown in Fig. is used; in this tool the sharp edge llic cuts the tube in two after it has been sealed off. To this purpose, other tools of suitable shape or both of them provided with cutting edges may be used, as obvious to those skilled in the art. Fig. la illustrates one form of mechanism which may be employed to actuate the tools 2 and 3. The lower tool jaws 2b and 3b comprise portions of conventional pivotally mounted clamping jaws H and I! which are opened and closed by'links I and I1. The upper jaws 2a and 3a are pivotally mounted on, and electrically'insulated from, the said clamping jaws l4 and I5 and are actuated through links l8, and I9 to compress the tool parts 2 and 3 in the manner shown in Fig. 3.

It must be further emphasized that numerous different shapes of tools can be used, for instance, tools which practically completely surround the tube I when pressed together. A dia-' grammatic plan of such an arrangement is shown in Fig. 6. The toolelements in this case are approximately of Z-shape and they are moved in the direction of the arrows 8 and 9 for compressing the tube i.

f that of the atmosphere, and provided with a tube Finally Fig. 7 shows how the auxiliary automatic machine 13 takes over the sealed-oi! lamp from the sealing-oi! position of rest no! the known automatic machine A upon which the incandescent lamps are produced. The tube cools down, together with the tool, at the position of rest 12 of the auxiliary automatic machine and is lifted oil at the position of rest 0 thereof after the drawing apart of the tool elements, which are brought back to their original condition again, either simultaneously or in the next position of rest of the auxiliary machine 13. In the meantime, or in a subsequent position of rest of the auxiliary machine, the tools can be coated with graphite suspension, preheated etc. without it being necessary for these purposes to reduce the speed of the main automatic machine or to increase the number of its positions of rest. Thus existing machines can readily be converted and put to good use for the purposes of my new process, as all the parts which serve for sealingoil. according to this invention are carried on the auxiliary machine B, which is positively driven by the motion work of the main automatic machine A. It is preferable that the directions of rotation of the main and auxiliary machines be opposite (as indicated by arrows II and I! in Fig. 7);

The process according to thisinvention may however also be carried out on a single automatic machine adapted for this purpose. An automatic machine of this kind is preferably so constructed that a sealing-off device suitable for carrying out the process of the invention is allotted to each individual one of its positions of rest. The advantage of this is that the several sealing-off tools actually come into action at much longer intervals of time than they do in the above described arrangement employing auxiliary automatic machines. The consequences of this are, on the one hand, that it is not necessary to change the tools so frequently and, on the other hand (as more time is available), that it is not compulsory in maintaining the requisite speed of working, to carry out the heating up and/or cooling down of the tools in a manner which will have a detrimental effect on the structure of the material of which they are made. Thus, in theselection of the material for the tools, a wider range is afforded when using the last-mentioned kind of automatic machines, and materials can be used which are more advantageous for reasons associated with the technics of glass working but which, when auxiliary automatic machines are employed, cannot stand up at all to the thermal stresses which arise in machines of this kind, or can do so only for a very short time.

I wish it to be understood that I do not desire to be limited to the exact ways of proceeding and apparatus shown and described, only to the sealing of vessels filled with gas under pressure greater than that of the atmosphere, for obvious modifications will occur to those skilled in the art.

In the claims affixed to this specification no selection of any particular modification is intended to the exclusion of other modifications thereof and the right to subsequently make claim to any modification not covered by these claims is expressly reserved.

Iclaim:

l. The process of sealingoffv a gas-filled vessel containing a gas under pressure greater than of vitreous material connected to the bulb of said vessel,'by sealing said tube, which, in a combined,

group of steps consists in placing a vessel with its tube between relatively movable and compressible resilient contact elements, heating said elements to a bright red heat, moving said elements into contact with a selected area of the tube intermediate the ends thereof whereby heat flows to said area from said elements by conduction, maintaining said elements in said heated condition and in contact'with said area until said area becomes sufliciently plastic to be compressed without breaking, resiliently pressing said elements against said area as it is being softened tocompress said area to close and seal said tube at said area, thereafter cooling the'closed tube and said resilient contact heating elements while still in contact with said closed tube, and after said tube is sufllciently resistant to withstand being blown out by the interior gas pressure,

compressing said elements. to partially release the same from contact with said tube and finally bodily removing said compressed elements from all contact with said tube.

2. The process of sealing-oil? a gas-filled vessel containing a gas under pressure greater than thatoi the atmosphere, andprovided with a tube of vitreous material connected to the bulb of said vessel, by sealing said tube, which, in a combined group of steps, consists in placing a vessel with its tube between two relatively movable U-shaped .sheet metal strips with curved ends to serve as compressible and resilient contact elements, heating said elements to a bright red heat, moving the curved ends of said elements into contact with a selected area of the tube intermediate the ends thereof whereby heat flowsto said area from said elements by conduction, maintaining said elements in said heated condition and the curved ends thereof in contact with said area until said area becomes sumcie'ntly plastic to be the same from contact with said tube and removing said compressed elements from said closed tube.

being softened to compress said area to close and seal said tube at said area, and subsequently closing and thereby also cutting in two said tube by means of said resilient contact heating elements, thereafter cooling the closed and severed parts of said tube still in contact with said resilient contact heating elements, and after the closed part of said tube connected with the bulb 01! said vessel is sufilciently resistant to withstand being blown out by the interior gas pressure, compressing said elements to partially release the same and thereby removing the eleof the two sheet metal plates bentto U-shape,

said sheet metal plates being positioned with their convex curved ends in opposed relationship so as to be capable of being pressed with said convex curved endsagainst said tubes, means for heating said sheet metal plates to at least bright red heat, and means connected to said pairs of jaws ior periodically moving said U-shaped plates into and out of contact with said tubes. a I

5. In an apparatus for sealing of! gas-filled vessels, each containing a gas under pressure greater than that of the atmosphere, by sealing the tubes of vitreous material each connected to the bulb of each of said vessels, the combination of 'tool means including two sheet metal strips capable of communicating the requisite heat for sealing of! said tubes exclusively by conduction,

two pairs of jaws, each of said pairs of laws holding the ends oi one sheet metal strip bent into U-shape, means connected to said pairs of jaws and adapted to movethem conjointly toward and away from each other, means connected with at least one jaw of each pair 01. jaws for moving it'relatively to the other jaw of the same said pair of jaws, and means for heating said sheet metal strips to at least bright red temperature when placed against said tubes.

6..In an apparatus for sealing ofl gas-filled vessels, each containing a gasr under pressure 3. The process of sealing-oft a gas-filled ves}.

sel containing a gas under pressure greater than that of the atmosphere, and provided with a tube of vitreous material connected to the bulbof said vessel, by sealing said tube, which, in a combined group of steps, consists in placing a vessel with its tube between. relatively movable and compressible resilient contact elements formed with means for separating said tube into two parts, heating said elements to a bright red heat, moving said elements into contact with a selected area of the tube intermediate the ends thereof whereby heat flows to said area from said elements by conduction, maintaining said elements in said heated condition and in contact with said area until said area becomes sufficiently plastic to be compressed without breaking, resiliently pressing said elements against said area "as it is greater than that of the atmosphere, by sealing the tubes of vitreous material each connected to the bulb of each of said vessels, the combination of elastically deformable sheet metal tools for applying the requisite heat for sealing oil? said tubes exclusively by conduction, means for moving said tools into and out of contact with said tubes, means for heating ,said'tools to at least bright-red heat, and means provided on part of said tools adapting the same to cut the closed tubes into two parts each upon being Pressed against said tubes at least at a red-hot temperature.

7. In an apparatus for sealing oil gas-filled vessels, each containing a gas under pressure greater than that of the atmosphere, by sealing the tubes of vitreous material each connected to the bulb of each of said vessels, the combination of elastically deformable sheet-metal tools for applying the requisite heat for sealing of! said tubes exclusively by conduction, said tools consisting of ametal alloy containing chromiumand another metal of the iron group in the periodic table, means for heating said tools at least to a red-hot temperature, and means for elastically and yieldably pressing said heated tools against said tubes.

8. In an apparatus for sealing ofi gas-filled vessels, each containing a gas under pressure greater than that of the atmosphere, by sealing the tubes of vitreous material each connected to the bulb of each of said vessels, the combination of heated tools adapted to compress the tubes and to impart the requisite heat for sealing off the same exclusively by conduction, means for moving the heated tools to compress said tubes, and means for heating said tools to at least bright red heat. each of said tools comprising an elastically deformable metallic part consisting of a strip of sheet metal positioned to contact the tube between the ends of the strip and connected at each end to the said means for moving the heated tools and adapted to be applied at least at bright-red-hot temperature against said tubes to compress said tubes at a rate corresponding to the softening of said tubes.

9. In an apparatus for scaling 011 gas-filled vessels, each containing a gas under pressure greater than that of the atmosphere, by sealing the tubes of vitreous material each connected to the bulb of each of said vessels, the combination of heated tools adapted to compress the tubes and to impart the requisite heat for sealing of! the same exclusively by conduction, means for moving the heated tools to compress said tubes, and means for supplying electric current to said tools to heat them to at least bright red heat, each of said tools comprising an elastically deformable metallic part consisting of a strip of sheet metal positioned to contact the tube between the ends of the strip and connected at each end to the said means for moving the heated tools and adapted to be applied at least at brightred-hot temperature against said tubes to compress said tubes at a rate corresponding to the softening of said tubes.

MIHALY nr: NEUMANN. 

